A data storage system may be implemented according to a storage technology referred to as the redundant array of independent disks (RAID). A RAID system includes one or more disk drives and an array controller connected to one or more computing systems. When several physical disks are set up to use RAID technology, the disks are said to be in a RAID array. This array distributes data across several disks, but the array is seen by the computer user and operating system as one single disk.
In some RAID implementations, data in conjunction with meta data (i.e., additional data used to validate the actual data) may be interleaved across a plurality of blocks on the disk drives. A concurrent series of blocks (one on each of the disks in an array) is collectively called a stride. Each stride of data is typically written across a plurality of disk drives in a single operation. This implementation generally improves data recovery and system efficiency, in case one of the disk drives fails or if data stored on one of the disk drives is corrupted.
The storage system may also include a storage cache that provides faster access to frequently or recently accessed data. Because space is limited in the storage cache, a storage cache controller may destage existing data from the storage cache to make room for new data that are to be copied to the cache according to a caching algorithm. Destaging refers to identifying data in the storage cache (e.g., by setting a corresponding dirty bit) to indicate that the data can be removed from the cache (e.g., after the data is written to the disk drives, or if it is determined that the cached data has not been updated since it was read from the disk drives).
In a RAID architecture, it is desirable to destage data from the cache in full strides because partial destaging of data in a stride is inefficient as it minimizes the amount of data that can be sequentially destaged from the cache. Full stride destaging is only possible when an entire stride is available in the storage cache. If the entire stride is not available, the storage cache controller may either wait for the entire stride to become available or alternatively destage a partial stride. Such an implementation is undesirable.
Systems and methods are needed that can overcome the above-noted shortcomings.